libcxx/test/std/utilities/variant/variant.variant/variant.status/index.pass.cpp

// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

// UNSUPPORTED: c++98, c++03, c++11, c++14

// <variant>

// template <class ...Types> class variant;

// constexpr size_t index() const noexcept;

#include <cassert>
#include <string>
#include <type_traits>
#include <variant>

#include "archetypes.hpp"
#include "test_macros.h"
#include "variant_test_helpers.hpp"

int main() {
  {
    using V = std::variant<int, ConstexprTestTypes::NoCtors>;
    constexpr V v;
    static_assert(v.index() == 0, "");
  }
  {
    using V = std::variant<int, long>;
    constexpr V v(std::in_place_index<1>);
    static_assert(v.index() == 1, "");
  }
  {
    using V = std::variant<int, std::string>;
    V v("abc");
    assert(v.index() == 1);
    v = 42;
    assert(v.index() == 0);
  }
#ifndef TEST_HAS_NO_EXCEPTIONS
  {
    using V = std::variant<int, MakeEmptyT>;
    V v;
    assert(v.index() == 0);
    makeEmpty(v);
    assert(v.index() == std::variant_npos);
  }
#endif
}